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# Modules

LangChain provides standard, extendable interfaces and external integrations for the following modules, listed from least to most complex:

#### [Model I/O](/docs/modules/model_io/)

Interface with language models

#### [Data connection](/docs/modules/data_connection/)

Interface with application-specific data

#### [Chains](/docs/modules/chains/)

Construct sequences of calls

#### [Agents](/docs/modules/agents/)

Let chains choose which tools to use given high-level directives

#### [Memory](/docs/modules/memory/)

Persist application state between runs of a chain

#### [Callbacks](/docs/modules/callbacks/)

Log and stream intermediate steps of any chain

#### [Experimental](/docs/modules/experimental/)

Experimental modules whose abstractions have not fully settled
